A hot glue gun is a tool for applying melted glue to a workpiece. The gun typically has an electric heating element for receiving a cylinder of solid glue. The solid glue is melted by the electric heating element as it passes through a heating chamber before being forced out of a nozzle for application to a workpiece. As the glue on the workpiece cools, the workpiece is secured to another object.
Mechanisms which advance the glue through the heating chamber and out of the nozzle are of two general types. The first type is that of a constant-pressure gun. In this mechanism a resilient element, typically a spring, applies a constant force to one end of the stick of glue. A valve in the nozzle prevents the glue from flowing through the nozzle until the valve is opened. The second kind of mechanism is an intermittent-pressure mechanism. This type of gun usually employs a trigger which must be squeezed to apply a force to advance the glue through the heating chamber and out of the nozzle.
The U.S. patent to Weller et al, U.S. Pat. No. 3,744,921, shows a hot glue gun of the constant-pressure type. In the Weller et al gun, a spring applies a continuous force to a plunger which applies pressure to a glue cylinder. A valve is located in the nozzle for automatic opening upon contact of the nozzle to a workpiece. When the valve is opened, melted glue flows through the nozzle and onto the workpiece.